Hi Nik,
OK if it is OBD2b then the following will need to be done to your loom.
At the ecu plug 'B' move pin B6 to the empty B23 location. Then un-pin B15 and tape it up out of the way, this wont be needed, but the pin itself could be useful so this may need cutting off.
I'm not sure if you have any spare plugs that you will be using for the extra loom sections needed but if not spade connectors would do.
On your original IAVC plug it will have 3 wires and the plug will be an oval shape, you need to unpin the wires from it and tape the orange one up out the way as this wont be needed. If you do have a round style plug for the vtec IAVC then you will need to pin the other two wires into it, the yellow and black wire will need to be at the top (where the release is on the plug)
Next up is the vtec wires.
Knock sensor will be first, on the ecu plug 'C' you will need to put a pin into location C3 then with a length of wire put it through the bulk head and either connect or original Honda round style plug (if you have spares) or use a spade connector and connect it the the knock sensor which is loacted at the top of the block slightly to the left just above the water hard pipe.
Nect is vtec pressure switch (this will only need to be done if your vtec solenoid has a round style connector on the side of it.
As per the knock sensor, on the ecu plug 'C' you will need to put a pin into location C10 and again running the wire through the bulk head and again if you have an original Honda round style plug attach it to this or your spade connector, the vtec pressure switch will also need to be earthed (i usually do it to where the original earth is on the gearbox but it is entirely up to you where it goes. Again I think the positive from the ecu will need to be at the top of the plug (where the release is) and the earth on the bottom but not 100% sure on this but trial and error is the way, if vtec doesn't work try swapping them over.
Next is the vtec solenoid.
On the ecu plug 'B' you will need to put a pin into location B12 and as before run it through the bulk head and to the vtec solenoid, like the knock sensor this is only one wire so pretty simple.
If you do all this and the car doesn't start (which it should if ecu is from a UK car) then you will need to switch the pins on ecu plug 'A' for the fuel pump relay. Swap the pin from location A16 to A15, this will solve your problem.
I have attached this image to make things easier for you.
If you need any more help just let me know.
Regards
Ben